A motor vehicle transmission typically uses multiple gear elements and plate-type friction clutches to couple input and output members of the transmission, and to thereby establish a desired output speed ratio. A hydraulic clutch piston compresses the plates of one of the friction clutches to transfer torque across the clutch, or to stop rotation of a node or powertrain element connected to one side of the clutch. In this manner, gear elements/nodes that are connected to the clutch can be held stationary to act as reaction members for transferring torque through the powertrain. Friction clutches may fully-applied, fully-released, or controlled with a variable rate of slip anywhere in between these two clutch apply states.
In some vehicle transmissions, a binary clutch is used in lieu of a friction clutch for certain purposes, such as for shifting the transmission into 1st gear low or reverse. Example binary clutches include dog clutches and selectable one-way clutches, the latter of which may use sprags, struts, or rollers to hold torque in one or two rotational directions as needed. Binary clutches may be used alone or in conjunction with rotating and/or braking friction clutches of the type noted above. Unlike conventional friction clutches, a binary clutch, as the name indicates, has only two possible clutch apply states, i.e., fully-applied and fully-released.